Catalytic treatment devices, known as catalytic converters, for treating internal combustion engine exhaust gasses, are known to deteriorate with use. Specifically, the efficiency with which the catalyst of catalytic treatment devices convert such engine exhaust gasses as carbon monoxide, oxides of nitrogen, and hydrocarbons decreases over the life of the treatment device and the light-off time of the device increases. Light-off time is the time required for a catalytic converter to reach a prescribed efficiency following a coldstart of the engine. Catalytic converter deterioration can result in increased automotive vehicle emissions. The increase in emissions can however, be mitigated to some extent by compromising other vehicle control strategies. Current vehicle control strategies are designed using a near worst case catalyst deterioration model, so that even near worst case catalyst deterioration, such as caused by worst case driving conditions, the treated engine emissions will still meet aggressive emissions control constraints. Worst case driving conditions are uncommon. As a result, many of the compromises made under worst case catalyst deterioration models are unnecessary to meet even highly ambitious emissions control constraints, such as for the vast majority of vehicles not exposed to the worst case driving conditions. Engine performance and fuel economy may be unnecessarily compromised using the current catalyst deterioration model.
It would therefore be desirable to avoid constraining automotive engine controls to the worst case catalyst deterioration model. It would be desirable to meet aggressive emissions control standards with minimum sacrifice to engine fuel economy and performance.